Method of injecting fuel into internal combustion engines



July 4, 1939. J, G. KIMMEL 2,164,684

METHOD OF INJECTING FUEL INTO INTERNAL COMBUSTION ENGINES Filed Feb. e,1957 mm... E A; e l

Vlllllllllll Patented July 4, 1939 UNITED STATES PATENT OFFICE METHOD FINJECTING FUEL INTO INTERNAL COMBUSTION ENGINES 6 Claims.

This invention relates to method of injecting fuel into internalcombustion engines.

In internal combustion engines of the type wherein fuel charges areinjected into the engines by external pressure, such as Diesel engines,two general methods of injection have been commonly employed, namely,air and mechanical injection. Mechanical injection is principallyemployed, especially in smaller engines, and is advantageous over airinjection since it eliminates the chilling effect on the fuel resultingfrom the expansion of air and because it eliminates the loss ofapproximately 10 per cent. in power, such power being required for theoperation of the compressor. On the other hand air injection isadvantageous for the reason that it provides thorough atomization of thefuel, which shortens the period for ignting the fuel after injection andthus assures more uniform burning of the fuel, but it requiresadditional compression of from 50 to 100 pounds over that required inmechanical injection to insure ignition.

Generally speaking, the principal object of the present invention is toprovide a method of injecting fuel into an internal combustion engine,

wherein the principal advantage of air injection, namely, fuelatomization, is retained, while eliminating the principal disadvantageof such system, namely, the chilling of the fuel.

More specifically, an object of the invention is to provide a method offuel injection for internal combustion engines which involves the use ofa fluid, which is normally a liquid, as the fuel injecting medium, andwherein such medium is used for injecting the fuel after beingvaporized,

or brought to the point of vaporization, by the application of heat at apressure in excess of the pressure in the cylinder.

A further object is the provision of a method for the injection andatomization of fuel oil in an internal combustion engine by utilizingthe hot vapor of a normal liquid under pressure in excess of that in theengine cylinder, the pressure andtemperature of the injecting fluidbeing maintained principally by the use of waste heat from the engine,thus effecting a .considerable saving in energy over the conventionalmethods of air injection.

A further object is to provide a method of injecting a heavy fuel oilinto an internal combustion engine by means of a light liquid fuel whichhas been heated to vaporization, or substantially to the point ofvaporization, at a pressure in excess of that in the engine cylinder.

Other objects and advantages of the invention will become apparentduring the course of the following description. y

In the drawing I have shown two embodiments of the inventionparticularly adapted for practicing the method. In this showing:

Figure 1 is a sectional diagrammatic view of the system, parts beingshown in elevation and parts being broken away,

Figure 2 is an enlarged vertical sectional view on line 2-2 of Figure 1,and,

Figure 3 is a sectional diagrammatic view showing a modified form oflever control means.

Referring to Figure 1, the numeral I0 designates a portion of aninternal combustion engine cylinder wall having a fuel injection openingII communicating with a needle valve seat I2. 'I'he cylinder wall isshown as being provided with a lateral or radial extension I3 in whichlis arranged a stem I4 carrying a needle Valve I5 at its inner endengageable with the seat I2.

The stem I4 is slidable in an opening I6 formed in the extension I3 andadjacent the outer end of the stem I4, this opening is substantiallyenlarged as at I1 to slidably receive a small piston I8, connected toand of greater diameter than the stem I4. Outwardly of the opening I1the extension I3 is provided with an enlarged opening I9 in which isarranged a compression spring 20 seated at its inner end against a head2| formed integral with the piston I8. A plug 22 is threaded in theouter end of the opening I9 in engagement with the spring 20. It will beapparent that this spring is of the compression type and of any desiredtension, and the normal tension of this spring may be adjusted byturning the plug 22.

A conduit 23 has its upper end communicating with the inner end of theopening or cylinder II and liquid under pressure is supplied through theconduit 23, in a manner to be described, to act against the inner end ofthe piston I8 to move the latter against the tension of the spring 20 toopen the needle valve I5. In this connection, it will be noted that whenthe needle valve I is seated, the inner end of the piston I8 is slightlyspaced from the inner end of the cylinder Il whereby fluid underpressure in the conduit 23 is free to act on the inner end of the pistonI8.

In accordance with the preferred practice of the invention, the fluidunder pressure in the conduit 23 is the liquid fuel oil which issupplied to the engine. The conduit 23 is provided with a branch passage24 which leads to the interior of the valve seat I2 to discharge fluidtherethrough into the cylinder I0 when the valve I5 is unseated. Ifdesired, a throttle valve 25 is provided in the passage 24.

siderable amount of vapor upon the release of pressure during or afterthe return stroke of`the pump plunger which supplies the fuel oil, and

` which will be described later.

A casing 21 contains the mechanism which supplies the fuel underpressure to the conduit 23.k Referring to Figure 1,it will be noted thatthe casing 21 is provided with a cylindrical opening 28 in which isarranged a sleeve 28 having a ange 35 intermediate its ends engageablqwith a shoulder 3I to limit the upward movement of the sleeve 23. Aspring 32 engages the lower face of the flange 30 to urge the sleeve 23upwardly, the lower end of this sleeve seating against the upper end ofa guide 33 in which the lower end of the sleeve 29 is slidable.

The sleeve 29 normally occupies the position shown in Figure 1 and itwill be noted that this.

- sleeve is provided with a port 34 which communicates through a port 35with al reservoir 38 formed within the casing 21. The port 34 admitsfuel oil into theinterior of the sleeve 29 under conditions to bedescribed, this port being in registration with the port 35 when thesleeve 29 is in the normal position shown in Figure 1. Moreover, theupper end of the sleeve 29 is spaced from the upper end of the cylinder23, when in normal position, thus presenting the area of the upper endof the sleeve 29 to fluid pressure in a manner to be described. 'Iheupper end of the cylinder 23 communicates with the lower end of theconduit 23 through a passage 31 An adjusting sleeve 38 is slidable inthe lower end of the guide 33 and is operative for limiting the downwardmovement of the sleeve 29. The lower end of the adjusting sleeve 38projects from the lower end of the casing 21 and is pivotally connectedas at 39 to one end of a. lever 45. This lever is pivotally connectedintermediate its ends as at 4| to a link 42 having its upper endpivotally supported by the casing 21 as at 43. The lever 40 may becontrolled in any desired manner to hold the adjusting sleeve 38 in anyadjusted position. It will be noted that the link 42 permits the linearmovement of the pivot 3l incident to axial adjustment of the adjustingsleeve 38.

In F'igure l manual means is illustrated as being operative foradjusting the position of the sleeve 33. A nut 44 has a pivot pin 45extending from Opposite sides thereof forengagement in the slots 45 ofthe arms of the lever 40. A stem 41 is threaded in the nut 44 andextends upwardly through an arm48 carried by the casing 21. Nuts 43 onopposite sides of the arm 48, prevent axial movement of the stem 41, andthis stem is provided at its upper end with an operating knob 5l).Obviously rotation of this knob moves the lever 4I to arrange theadjusting sleeve 38 in any desired position.

A pump plunger I is reciprocable in the sleeves 29 and 38. This plungeris provided in its upper end with an axial passage 52 communicating atits lower end with a lateral passage 53 adapted at the end of thepumping stroke to communicate with a port 54 formed in the sleeve 23.This port, in turn, is in constant communication with a small passage 55leading to a small cylinder 55. A cylinder 51 of reduced diameterextends above the cylinder 55 and receives a slidable stem 58 having a.Ismall piston 53 at its lower end operating in the cylinder 55.

The upper end of the stem 53 terminates in a valve 50 normally engaginga valve seat 5I, and a compression spring 82 normally urges the valve 50against its seat. It will be noted that the upper end of the smallpiston 59 is arranged slightly below the upper end of the cylinder 58when the valve 6I is in engagement with its seat, and accordingly thearea of the upper end of the piston 53-.around the stem 55 is free to besubjected to the. pressure of fluid discharged through the passage 55 ina manner to be described.

The valve 5l controls a port 63 communicating with a passage 54 leadingto the reservoir 38. This reservoir is supplied with fuel oil through a.pipe 55, and the mechanism including the pump plunger 5I operates topump fuel oil through the passage 23 and to return fuel therefrom to thereservoir 35 upon the seating of the valve I5. lll'or the latterpurpose, a by-pass conduit 55 has one end communicating with the passage23 and its other end communicating with the cylindrical opening 51 toreturn fuel oil to the reservoir when the valve 60 is opened in a mannerto be described.

The lower end of the pump plunger projects a substantial distance belowthe casing 21 and is provided at its lower end with a. roller 61engaging a cam 68 carried by a shaft 69. A relatively light spring 51'is employed for urging the plunger 5I downwardly. The shape of the camis preferably such as to impart relatively rapid movement to the plunger5I at the beginning of the fuel injection in order to obtain a quickopening oi' the injection valve, as will become apparent. During thelatter part of the pumping stroke of I the plunger, the rate of movementof the plunger need be only suiliciently rapid as to'pump oil at therate at which the oil is injected into the engine. For this purpose, thecam Il is shaped substantially as shown in Figure 1 and is rotatable inthe direction of the arrow.

Adjacent the valve seat I2, the projection I3 is provided with anannular passage to which the injecting fluid is supplied through a pipe1I. The injecting fluid, as it passes from the passage through theinjector nozzle, is in the form of a heated gas which may be heated air,or it may be heated hydrogen or some other combustible gas. Morespecifically, the injecting fluid is preferably a readily vaporizablenormally liquid fuel such as a light hydrocarbon, or a derivative of ahydrocarbon such as alcohol, and as will be further explained, such fuelmay be supplied to the annular passage 1II in gaseous form, or at suchtemperature and pressure that it will be immediately converted intogaseous form promptly upon the opening of the `injection valve. Stillmore specifically, the injecting fluid is preferably alcohol, and suchfluid is preferably supplied to the passage 10 in the neighborhood of orslightly above its critical temperature and critical pressure.

Means are employed for subjecting the injecting fluid to the action ofheat and pressure to supply the fluid to the passage 10 in the desiredphysical condition. A pipe 12 is connected to a suitable source ofinjecting fluid such as alcohol, and a suction valve 13 controlscommunication between the pipe 12 and a pump chamber 14. A pump cylinder15 communicates with the chamber 14 and is provided with a reciprocatingpump plunger 16 which may be actuated from any suitable source. It alsowill be apparent that the pump is illustrated only diagrammatically andthat any suitable type of pump may be employed.

Upon upward movement of the plunger 16 as illustrated in Figure 1, theinjecting fluid will be drawn into the chamber 14 from which it will beexpelled upon downward movement of the plunger into an outlet pipe 11,past a discharge valve 18. The pump obviously may be of such capacity asto satisfy the maximum demands of the motor, and accordingly excessinjecting fluid is pumped under most conditions. To take care of theexcess fluid, a. by-pass return pipe 19 is connected between the pipes11 and 12, and a relief valve 80 controls communication through the pipe19 to determine the pump outlet pressure at which the fluid will beby-passed to the supply pipe 12. The relief valve may be of anyconventional type, and is adjustable as to its opening pressure by meansof a handle 8|.

The pipe 11 leads to one end of a coil 82 arranged in a jacket 83connected in the exhaust pipe 84 of the engine. The other end of thecoil 82 is connected by a pipe 85 with the interior of a heating casing86 in which is arranged an electrical heating unit 81. The electricalheating device is preferably employed for the purpose of heating theinjecting fluid upon the starting of the motor, and a suitable portionof the apparatus, such as the pipe 85, may be provided with aconventional thermostat 88 for cutting out the heating coil 81 after theengine has been running 1 a sufficient length of time to properly heatthe injecting fluid passing through the coil 82. Accordingly it will beapparent that the heating coil 82 and associated elements constitute thenormal heating means for the injecting fluid, and that the fuel may besupplied under pressure to the injector nozzle by means of the pumpdescribed, the relief valve 80 and its adjustment determining thepressure of the injecting fluid supplied to the nozzle in accordancewith the fluid being employed.

As previously stated, any suitable means may be employed for adjustingthe vertical position of the sleeve 38, and in Figure 1 manuallyoperable means has been illustrated for this purpose. If desired, thesleeve 38 may partake of vertical adjustment according to the speed ofoperation of the engine. In Figure 3 .a shaft 89, suitably driven by theengine, carries a conventional governor 90 having a lower verticallyslidable collar 9I connected by a link 92 to the free end of the lever40. As will become apparent, increases inengine speed thus may beutilized to reduce the total injection of fuel into the engine at eachoperation of the injecting means.

The operation of the apparatus is as follows:

As previously stated, the collar 38 may be arranged in desired adjustedpositions, the purpose of which will become apparent. Assuming that thecollar 38 is xed in a predetermined position with the engine operationbeing initiated, the rotation of the shaft 69 causes the cam 68 toreciprocate the pump plunger I to effect the fuel injection operation;while the injecting fluid will be heated by the electric heating element81.

Assuming the parts to be in the positions shown in Figure 1 it will beapparent 4that fuel will be present in the interior of the upper end ofthe sleeve 29, and also in the conduit 23 and passage 58, fuel beingadmitted through the ports 34 and 35. Rotation of the shaft 69 in acounter-clockwise direction causes the cam 68 to lift the plunger 5I,and initial movement of this plunger causes its upper end to move acrossthe port 34 and thus close communication between the interior of theupper end of the sleeve 29 and the reservoir 38 in which the relativelyheavy fuel oil is maintained, fuel being constantly supplied to thereservoir through the pipe 65.

After the port 34 is closed, continued upward movement of the plunger 5Isubjects the fuel above the plunger to pressure which reacts against thearea of the upper end of the sleeve 29 to cause this sleeve to movedownwardly against the tension of the spring 32. 'Ihe tension of thisspring need be sufficient only to returnV the sleeve 29 to its upperposition upon the' completion of the pumping operation. The pressureexerted on the upper end of the sleeve 29 causes the latter to movedownwardly until the lower end of the sleeve contacts with the upper endo-f the adjusting sleeve 38, whereupon further downward movement of thesleeve 29 is arrested. Continued upward movement of the plunger 5|immediately increases the pressure in the body of the fuel above theplunger, and this pressure acts against the inner face of the piston I8,thus causing the piston and the elements carried thereby to be moved tothe right as viewed in Figure 1 against the tension of the spring 20.This action unseats the needle valve I5 and fuel under pressure ispumped from the conduit 23 through the passage 24 and thus into theinjection nozzle.

During this operation it will be apparent that the pump plunger 16 willbe operating and from the plunger to the injection nozzle the injectionfluid will be maintained under substantial pressure. Therefore, when theneedle valve I5 is retracted under the influence of the pressure of therelatively heavy fuel oil, the injection fluid will be discharged fromthe annular passage through the nozzle II, thus injecting the propercharge of fuel into the engine.

The working stroke of the plunger 5I will be determined by the positionof the adjusting sleeve 38, which limits the downward movement of thesleeve 29. Prior to the point at which the plunger 5I reaches the upperlimit of its stroke, which point will be determined by the position ofthe sleeve 38, as will become apparent, the port 53 of the plunger willcome into registration with the port 54 whereupon uid under the pressuregenerated by the pumping action will flow through the axial passage 52of the plunger, and thence through port 53 and passage 55 into the smallcylinder 56. The pressure in the liquid in the cylinder 56 acts againstthe upper exposed surface of the piston 59, whereupon this piston willbe moved downwardly against the tension of the spring 62 to unseat thevalve 80. The accumulated pressure in the conduit 23 and passage 66, andthe fuel oil-containing spaces in communication therewith, will berelieved and oil will flow from the passage 66 through port 63 andthence back into the reservoir 36 (Figure 2) through the passage 84. Thepressure acting against the inner end of the piston I8 thus will bereleased, and the spring 20 will seat the needle valve I5.

Upon subsequent downward movement of the plunger 5I, the initialmovement will close communication between the ports 53 and 54, followed75 by the upward movement oi the sleeve 29 to the normal -position shownin Figure l. As the plunger 5I approaches its lower limit of movement,additional fuel oil will be admitted into the upper end of the plunger29 through the port 34, and when the plunger reaches its lower limit ofmovement, pressure above the piston head 59 is released through the port54 to permit the valve 60 to close, the upper end of the port 54extending slightly above the upper limit of the plunger 5i when thelatter is in its lowermost position. The foregoing operation is thenrepeated during the next rotation of the cam shaft 69, as will beapparent. The cycle of operation obviously is repeated throughout theoperation of the engine. l

The hot exhaust gases passing through the pipe 84 and jacket 83 heat theinjection fluid in the coil 82, such fluid being discharged into thecasing 86 through the pipe 85. When the fluid flowing through the pipereaches the desired temperature, the thermostat 88 will break thecircuit through the heating unit 81, whereupon the injection fluid willbe maintained at its proper temperature by the exhaust gas heater.

Assuming that it is desired to increase each fuel charge, the knob 50may be turned to lower the free end of the lever 40, thus elevating theadjusting sleeve 38. It will be apparent under such conditions that ashorter portion of the pumping stroke of the piston 5I will be taken upin moving the sleeve 29 downwardly, and a greater portion of the pumpingstroke will be utilized for injecting the successive charges into theengine by maintaining the needle valve I5 open for longer periods. Inthis connection, it will be noted that the shorter the downward strokeof the sleeve 28 in accordance with the position of the adjusting sleeve38, the, longer will be the pumping stroke of the plunger 5I before theport 53 uncovers the port 54 to release the pressure in the pumped fueloil.

Conversely, the fuel charges may be reduced by adjusting the sleeve 38to a lower position. In such case a greater portion of: the pumpingstroke of the plunger will be utilized in forcing the sleeve 29downwardly and a lesser portion will be utilized in retaining the needlevalve I5' in open position. Likewise, the longer the movement of thesleeve 29, the sooner the port 53 will uncover the port 54 to relievethe pressure in the pumped fuel oil. Thus the individual fuel chargesmay be reduced as desired.

The relationship between the areas of the upper end of the sleeve 29 andthe upper end of the plunger 5I fixes the relationship between thebeginning and the end of the injection, Assuming, under normal speed,that injection starts 10 degrees, crank travel, before dead center andends 30 degrees after dead center, the engine speed may be reduced bylowering the sleeve 38. If the area of the upper end of the sleeve 29equals the area of the upper end of the plunger 5I, both the sleeve andplunger will have moved the same distance when the sleeve 29 comes torest upon the upper end of the sleeve 38, and the beginning of injectionwill be retarded to the same extent that the end of the period ofinjection has been advanced. Assumed, in order for the engine to idle,that the period of injection must be reduced to lil degrees cranktravel. In the present construction, adjustment may be made so thatinjection will start 5 degrees after dead center and end l5 degreesafter dead center.

' In such case, the area of the end ofthe sleeve 29 should be less thanthe area of the end of the plunger 5i, whereby the sleeve 28 will moveat a higher speed than the plunger 5i, and injection will not beretarded as much as the end of the injection period will lbe advanced.The relative areas of the upper ends of the sleeve 29 and plunger 5Ireadily can be designed so that injection will not start later than deadcenter under all operating positions of the sleeve 38, which is a vitalrequirement, and a suitable injector can be made for any kind of engineor engine speed.

For example, a small high speed engine will require a retardation of theopening of the injector valve nearly equal to the advancing of the timeof valve closure. On the other hand a large slow speed engine can standonly a small retardation of the time of the opening of the injectionvalve, and the injection period must be shortened principally byadvancing the time of. valve closure.

The form of the invention shown in Figure 3 is the same in principle asthe form shown in Figure l except that it employs an engine drivengovernor for determining the position of the sleeve 38. Thisconstruction may be desired in installations where an engine is to bedriven at a relatively constant speed.

In order to adapt the rate of injection to varying conditions, thethrottle valve 25 may be employed in the passage 24, although its useordinarily is unnecessary. 'I'he valve 25 may be omitted where the rateof fuel consumption is fairly uniform, in which case the cross-sectionalarea of the passage 24 will be predetermined in accordance with theparticular nozzle. The check valve 26 may be employed in the passage 24if the relatively heavy fuel oil contains suilicient low boilingfractions to form a considerable amount of vapor upon the release ofpressure after the port 53 comes into registration with the port 54.

As previously stated, engines of the fuel injection type, such as Dieselengines, commonly employ either of two methods of injection, namely, airpressure and mechanical, and the former is advantageous over the latterin that it provides more perfect atomization of the fuel. Air injectionas it has been consistently practiced, has been found to bedisadvantageous because of the chilling eiect incident to adiabatic heatlosses occurring upon the expansion of the air.

In accordance with the present method I have found that if relativelyhighly heated gases are supplied to the annular passage 'l0 at pressuresabove the internal pressure of the engine at the point at whichtheneedle valve l5 is opened, highly advantageous results can beobtained. For example, relatively highly heated air may be supplied tothe passage 'l0 at a pressure above the internal pressure of the engineand upon the opening of the needle valve l5, the injecting iiuid willinject a fuel charge without heat losses suftlcient to chill the fueland thus result in the substantial loss in power incident to theconventional operation of a Diesel type engine.

Further increased emciency can be accomplished by employing acombustible gas such as hydrogen by introducing it in the manner previously described, e. by supplying the gas in a heated condition and at amaintained pressure above that of the internal pressure of the engine.In such case, the relatively highly heated hydrogen also prevents thechilling or condensation oi the relatively heavy iuel oil suppliedthrough the passage 24, and provides` perfect atomizatlon with lil theaccompanying reduction in the delay period for igniting the fuel afterinjection. Thus increased efficiency is provided in the engine byassuring a more uniform burning of the fuel and therefore a more uniformproduction of power,

As the injection medium, I may use water, but l prefer to employ one ofthe lighter hydrocarbons such as gasoline or benzine or a derivative ofhydrocarbon such as an alcohol. Where the expression hydrocarboncompound is employed in the claims, therefore, this expression isintended to cover volatile compounds of both the hydrocarbon and alcoholgroups. When such a compound is employed as the injection medium, thepressure and temperature of the medium are so related to each other thatthe pressure Will be at the vaporization point for the predeterminedtemperature, and above that of the internal pressure in the engine.However, the pressure may be slightly below or above that of thevaporization point at the predetermined temperature, so long as it ismaintained above the necessary injection pressure.

Where the expression normal liquid is employed in the claims, thisexpression is intended to mean a fluid which is liquid at ordinary orroom temperatures such as the hydrocarbons and derivatives thereofreferred to above.

More specifically, I prefer to employ alcohol, such as ethyl alcohol, asthe injection medium because of its high eiciency in the present system,and because of its suitable and easily maintained relatively lowcritical temperature and pressure. When alcohol is employed, it ispreferred that it be maintained approximately at its criticaltemperature and pressure, and it Will be apparent that upon each openingof the needle valve I5, the alcohol in gaseous form Will be dischargedthrough the injector nozzle together with the proper charge of theheavier fuel from the passage 24.

It will be apparent that the apparatus described is partitcularlyadvantageous for use in the practice of the method, and that theapparatus is relatively simple and easily adjusted and controlled.Relatively heavy fuel oil may be advantageously employed and willprovide a high degree of operating efficiency. The lfloating sleeve 29and its control means provide, in conjunction With the pump plunger l, ahighly effective means for determining each fuel charge. and each fuelcharge may be quickly and readily adjusted by the means for verticallymoving the sleeve 38.

It is to be understood that the methods herein described are to be takenas preferred examples of the same and that various changes in thepractice of the method may be made without departing from the spirit ofthe invention or the scope of the subjoined claims.

I claim:

1. The method of injecting fuel charges into an internal combustionengine cylinder through an injection nozzle, which comprises supplying arelatively heavy hydrocarbon fuel oil to the nozzle, and subjecting itto the injection action of a normal liquid approximately at its criticaltemperature and critical pressure.

2. 'Ihe method of injecting fuel charges into an internal combustionengine cylinder through an injection nozzle, which comprises supplying arelatively heavy hydrocarbon fuel oil to the nozzle, and subjecting itto the injection action of a normal liquid above its criticaltemperature and critical pressure.

3. The method of injecting fuel charges into an internal combustionengine cylinder through an injection nozzle, which comprises supplying arelatively heavy hydrocarbon fuel oil to the nozzle, and subjecting itto the injection action of a lighter hydrocarbon compound in liquid format a pressure in excess of the pressure within the engine cylinder atthe time of injection and at a temperature approximately at the point ofvaporization at such pressure.

4. The method of injecting fuel charges into an internal combustionengine cylinder through an injection nozzle, which comprises supplying arelatively heavy hydrocarbon fuel oil to the nozzle, and subjecting itto the injection action of a lighter hydrocarbon compound in liquid format a pressure in excess of the pressure within the engine cylinder atthe time of injection and at a temperature above the point ofVaporization at such pressure.

5. The method of injecting fuel charges into an internal combustionengine cylinder through an injection nozzle, which comprises supplying arelatively heavy hydrocarbon fuel oil to the nozzle, and subjecting itto the injection action of a lighter hydrocarbon compound approximatelyat its critical temperature and critical pressure.

6. The method of injecting fuel charges into an internal combustionengine cylinder through an injection nozzle, which comprises supplyinga.

relatively heavy hydrocarbon fuel oil to the nozzle, and subjecting it'to the injection action of a lighter hydrocarbon compound undertemperature and pressure conditions approximating critical conditions,at least one of such conditions being above the critical point.

JOSEPH G. KIMMEL.

